Robust synchronization of coupled circadian and cell cycle oscillators in single mammalian cells.

Circadian cycles and cell cycles are two fundamental periodic processes with a period in the range of 1 day. Consequently, coupling between such cycles can lead to synchronization. Here, we estimated the mutual interactions between the two oscillators by time-lapse imaging of single mammalian NIH3T3 fibroblasts during several days. The analysis of thousands of circadian cycles in dividing cells clearly indicated that both oscillators tick in a 1:1 mode-locked state, with cell divisions occurring tightly 5 h before the peak in circadian Rev-Erbα-YFP reporter expression. In principle, such synchrony may be caused by either unidirectional or bidirectional coupling. While gating of cell division by the circadian cycle has been most studied, our data combined with stochastic modeling unambiguously show that the reverse coupling is predominant in NIH3T3 cells. Moreover, temperature, genetic, and pharmacological perturbations showed that the two interacting cellular oscillators adopt a synchronized state that is highly robust over a wide range of parameters. These findings have implications for circadian function in proliferative tissues, including epidermis, immune cells, and cancer.

Major Empson sur AV, pesage de Paris-Nice [cycle-car, 1100 cmc, course Paris-Nice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 57958

Baudelocque sur Morgan [cycle-car, 1100 cmc, course Paris-Nice] : [photographie de presse] / [Agence Rol]

Référence bibliographique : Rol, 57960

Repercussion of a deficiency in mitochondrial ß-oxidation on the carbon flux of short-chain fatty acids to the peroxisomal ß-oxidation cycle in Aspergillus nidulans.

The fungus Aspergillus nidulans contains both a mitochondrial and peroxisomal ß-oxidation pathway. This work was aimed at studying the influence of mutations in the foxA gene, encoding a peroxisomal multifunctional protein, or in the scdA/echA genes, encoding a mitochondrial short-chain dehydrogenase and an enoyl-CoA hydratase, respectively, on the carbon flux to the peroxisomal ß-oxidation pathway. A. nidulans transformed with a peroxisomal polyhydroxyalkanoate (PHA) synthase produced PHA from the polymerization of 3-hydroxyacyl-CoA intermediates derived from the peroxisomal ß-oxidation of external fatty acids. PHA produced from erucic acid or heptadecanoic acid contained a broad spectrum of monomers, ranging from 5 to 14 carbons, revealing that the peroxisomal ß-oxidation cycle can handle both long and short-chain intermediates. While the ∆foxA mutant grown on erucic acid or oleic acid synthesized 10-fold less PHA compared to wild type, the same mutant grown on octanoic acid or heptanoic acid produced 3- to 6-fold more PHA. Thus, while FoxA has an important contribution to the degradation of long-chain fatty acids, the flux of short-chain fatty acids to peroxisomal ß-oxidation is actually enhanced in its absence. While no change in PHA was observed in the ∆scdA∆echA mutant grown on erucic acid or oleic acid compared to wild type, there was a 2- to 4-fold increased synthesis of PHA in ∆scdA∆echA cells grown in octanoic acid or heptanoic acid. These results reveal that a compensatory mechanism exists in A. nidulans that increases the flux of short-chain fatty acids towards the peroxisomal ß-oxidation cycle when the mitochondrial ß-oxidation pathway is defective.

Increasing the carbon flux toward synthesis of short-chain-length--medium-chain-length polyhydroxyalkanoate in the peroxisome of Saccharomyces cerevisiae through modification of the beta-oxidation cycle.

Short-chain-length-medium-chain-length polyhydroxyalkanoates were synthesized in Saccharomyces cerevisiae from intermediates of the beta-oxidation cycle by expressing the polyhydroxyalkanoate synthases from Aeromonas caviae and Ralstonia eutropha in the peroxisomes. The quantity of polymer produced was increased by using a mutant of the beta-oxidation-associated multifunctional enzyme with low dehydrogenase activity toward R-3-hydroxybutyryl coenzyme A.

Full diversity product codes for block erasure and block fading channels

We show how to build full-diversity product codes under both iterative encoding and decoding over non-ergodic channels, in presence of block erasure and block fading. The concept of a rootcheck or a root subcode is introduced by generalizing the same principle recently invented for low-density parity-check codes. We also describe some channel related graphical properties of the new family of product codes, a familyreferred to as root product codes.

Vertical Product Differentiation, Entry-Deterrence Strategies, and Entry Qualities, September 2005

We analyze the entry of a new product into a vertically differentiated market in which an entrant and an incumbent compete in prices. Here the entry-deterrence strategies of the incumbent firm rely on “limit qualities.” With a sequential choice of quality, a quality-dependent marginal production cost, and a fixed entry cost, we relate the entry-quality decision and the entry-deterrence strategies to the level of entry cost and the degree of consumer heterogeneity. Quality-dependent marginal production costs in the model entail the possibility of inferior-quality entry as well as an incumbent’s aggressive entry-deterrence strategies of increasing its quality level toward potential entry. Welfare evaluation confirms that social welfare is not necessarily improved when entry is encouraged rather than deterred.

Managing Quality under Heterogeneous Consumer Demand and Product Quality, October 2005

Based on accepted advances in the marketing, economics, consumer behavior, and satisfaction literatures, we develop a micro-foundations model of a firm that needs to manage the quality of a product that is inherently heterogeneous in the presence of varying customer tastes or expectations for quality. Our model blends elements of the returns to quality, customer lifetime value, and service profit chain approaches to marketing. The model is then used to explain several empirical results pertaining to the marketing literature by explicitly articulating the trade-offs between customer satisfaction and costs (including opportunity costs) of quality. In this environment firms will find it optimal to allow some customers to go unsatisfied. We show that the relationship between the expected number of repeated purchases by an individual customer is endogenous to the choice of quality by the firm, indicating that the number of purchases cannot be chosen freely to estimate a customer’s lifetime value.

Katepillarista kauppakassiin : product placement suomalaisessa tv-ohjelmatuotannossa

Product placement has become more and more common in Finnish television programmes lately. Product placement, as with the whole of the television industry, is strictly regulated and monitored by law. Surreptitious advertising, sponsorship, cooperative partnerships and product placement are often confused with each other. Partially these activities are interpenetrative. Present legislation doesn't recognise product placement, therefore it doesn't have any specific position in law, thus causing problems. Product placement in domestic tv-programmes is still relatively modest. More extensive activity is perceivable at the movies where the restrictions are considerably more liberal. In the United States, product placement is a part of a production's budget. Pressure to increase financing has grouwn in both Finland and Europe. There has been considerable preparation in advance of a new television directive in the European Union which would allow more liberal advertising and product placement as a part of financing tv-programmes. The proposal for a new directive is currently only on its first round so product placement probably won't become better defined in law in the near future. Finnish television producers were interviewed as part of the research for this thesis, in order to clarify product placement position and usage in domestic televion programmes. Surreptitious advertising, sponsorship, different kinds of cooperative partnerships and the need for guidance were also discussed in the course of the themed interviews. Even though product placement does not currently play a significant part in the financing of a production, there are certainly pressures in that direktion. In the field of television, the legal boundaries of product placement are presently being explored in order to assess its position as a part of budgeting and covering expenses.

Measurement with Some Theory: a New Approach to Evaluate Business Cycle Models

We propose a method to evaluate cyclical models which does not require knowledge of the DGP and the exact empirical specification of the aggregate decision rules. We derive robust restrictions in a class of models; use some to identify structural shocks and others to evaluate the model or contrast sub-models. The approach has good size and excellent power properties, even in small samples. We show how to examine the validity of a class of models, sort out the relevance of certain frictions, evaluate the importance of an added feature, and indirectly estimate structural parameters.